The invention relates to compositions and methods used in the formation of a polymer coating from a polymer particulate. The coatings of the invention can be made in a uniform continuous structure. Further, floor finishes having appropriate predetermined properties such as hardness, thickness, resiliency, and integrity can be made. One aspect of the invention is a two part coating system. A second aspect of the invention is a method for forming the polymer coating of the invention using the two part system and a number of distinct coating forming protocols. Another aspect of the invention is a floor finish system that results in substantial labor savings.
Coating compositions are generally well known and have been formulated using a variety of technologies such as solvent based, aqueous liquid and powder systems. Powder coatings have been electrostatically applied to hard surfaces such as metals and then baked into a hard resistant finish. Reactive liquid coatings have been made by combining reactive materials (such as reactive isocyanates, ethylenically unsaturated reactive systems, reactive epoxy systems, etc.). Such systems have been applied to surfaces and then reacted to form a crosslinked hard surface. Further, coatings have been formed by dissolving typically polymeric materials in organic solvents at a solids concentration of about 10 to 50 wt.-%. Such solutions are applied and the solvent borne materials dry to a hard surface by the evaporation the solvent leaving a polymer coating. In order to increase the add-on of polymeric solids, polymer materials have been dispersed in aqueous media to form finish compositions. Lastly, aqueous technologies are used with active materials at concentrations typically higher than solvent systems. Such aqueous dispersions have been applied to surfaces for the purposes of forming a finish layer by serial application and evaporation of the water. Once the water is removed, the polymer materials form a useful film typically in a multi-coating layer. Solvent or aqueous based systems typically leave a residue of the medium in the coating.
Typical compositions and methods include those in Michio et al., Japanese Patent No. 92243309A. Michio et al. teach a aqueous/solvent coating composition for floors comprising a polymeric material combined with an ether solvent material adapted for reduced odor. Feigin, U.S. Pat. No. 4,131,585, teaches a polyether leveling agent adapted for use in aqueous self-polishing, dry bright coating compositions. Hackett et al., U.S. Pat. Nos. 4,363,835 and 4,704,429 and Zdanowski et al., U.S. Pat. No. 4,517,330, teach a method of forming floor finishes by applying an aqueous dispersion of polymer and materials and then dry buffing the resulting coating at high temperature to either fuse or crosslink the waxy or reactive coating composition. Bolgiano et al., U.S. Pat. No. 4,421,782, teach the formation of a coating from an aqueous system which after drying is radiation cured into a hard tough surface. Craven, U.S. Pat. No. 3,776,752, teaches compositions and methods for finishing surfaces. The method comprises applying a solvent dispersion of a polymer coating material, drying the applied material to form a coating and then forming the resulting coating with a finishing agent. Such finishing agents disclosed by Craven include typical plasticizing compositions. Lovell, Canadian Patent No. 717,495 (U.K. Patent No. 930,919), teaches the application of an organosol polish composition. Lovell discloses that the organosol material, when cosprayed with a solvent material, forms a combined coating which dries to a hard floor surface. Lewis et al., U.S. Pat. No. 4,168,255, and Gehman et al., U.S. Pat. No. 4,017,662, teach a polishing method involving the application of an aqueous coating composition containing a polymer material and finish forming agents. The polymeric materials combine with the agents as the aqueous material evaporates leaving a hard floor finish. Berrido, U.S. Pat. No. 4,747,880, teaches a dry granular floor care product. The dry granular material is formulated such that it can be combined with water to form an aqueous solution or dispersion which can be applied to form a clean shiny appearance after drying.
The prior art coating technology involves heat melted or fused coatings, reactive crosslinking coatings, or coatings that rely on a carrier liquid, an evaporating liquid aqueous or solvent medium for film formation. Such media involve solvents which must evaporate upon application to initiate coalescence of the finish layer. Further the prior art aqueous compositions typically require two or more applications to form a finished surface having two or more distinct layers for a complete floor treatment. The typical applications of coatings to floors, walls, ceilings and other environmental hard surfaces can involve rolling, mopping, spray coating and other conventional methods. A combination of a resin, solvent (aqueous or organic), diluent, additives and pigment can be used. A survey of conventional coating composition and techniques is shown in Kirk-Othmer Concise Encyclopedia of Chemical Technology, Fourth Edition, Wiley Interscience Publications, pp. 469-482 (John Wiley and Sons, Inc. 1999).
A need exists for floor coating systems that can be used with minimal labor in forming a reliable coating with as little as one application of the coating system. The coating systems of the invention can be used without substantial heat input for curing or a substantial proportion of an organic carrier solvent or an aqueous medium.
We have found a two-part system that can be used in a method for forming a continuous hard durable coating on virtually any surface. The two-part system comprises a polymer first part in the form of a finely divided flowable powder or particulate that can be delivered to a surface without an aqueous or organic solvent or other carrier liquid. The second part is a liquid part comprising a liquid coalescent or coalescing agent. In use, the parts are combined on the floor surface or as they are being delivered to the floor surface. The coalescing agent causes the polymer powder uniformly distributed in a finely divided state to coalesce and form a uniform film or coating within a short time after it came in contact with the coalescent. The materials can be applied in one of three application regimens we have defined to date; others may be developed and used. The powder can be uniformly placed on a target surface first followed by a careful uniform application of the coalescing agent. Second, the coalescing agent can be placed on the target surface followed by a careful uniform application of the powder particle. Lastly, the materials can be formed into a fine dispersion of the material in air, combined in an application device and simultaneously delivered to the surface. In such a process, the powder and coalescing agent can be atomized in separate atomizers and combined after atomization to form a spray of the final coating components.
One important application of the coating technology of this invention is to form hard, uniform coatings with regular thickness and integrity on floors. These coatings are typically 1 to 20 microns, preferably 3 to 12 microns, most preferably 4 to 10 microns in thickness. The floor finishes can have properties such as hardness, thickness, resiliency, integrity and wear resistance that meet or exceed requirements of current floor finish technology. Two or more coatings can be made if each coating provides a unique property. Layers of different hardness can be used. A first layer can be formed from a colored layer with a second uncolored clear layer. A first layer can be used with a second layer having a COF additive or biocide. A first acrylic layer can be used with a second urethane layer.
Floor surfaces that can be treated include installed floors, uninstalled sheet vinyl or uninstalled flooring units. The coatings can be applied during manufacture of the flooring as one of the final steps in manufacture, can be applied to the flooring at an installation site just prior to installation, or can be applied to the floor after installation or during routine maintenance. The primary substrates or supports for conventional coating systems include paper and paperboard, polymer films such as polyethylene, polyethylene terephthalate, metal foils, woven and non-woven fabrics, fibers, metal coils and a variety of environmental surfaces including floors, walls, ceilings, hard surfaces, exterior walls and other rough, curved or flat surfaces. Each of these kinds of surfaces utilizes coating compositions and methods adapted for each coating environment. Many coating processes are used in the industry including methods that create single and multiple layers. The precision and uniformity of the coating is important for consistent coverage, uniform appearance and wear properties.
For the purpose of this patent application, the term xe2x80x9ccoatingxe2x80x9d refers to a single or multiple coating of a polymer material in a substantially uniform layer. In this application uniform indicates the thickness does not vary more than about xc2x13 microns, preferably xc2x12 microns, from place to place in the coating. Such a coating can be applied under factory conditions or in the field. The term xe2x80x9cfloor finishxe2x80x9d typically connotes a floor coating having a thickness of greater than 1 micron but typically less than 12 microns, preferably less than 5 microns having a single layer formed from the coalesced distribution of the polymer particles. Such floor finishes can be applied during floor tile manufacture or at a building location. Traditional floor finish methods use multiple (typically 4 or 5) applications of the finish forming liquid to result in a multi-layer or laminate structure. Each layer typically has a thickness less than 2 microns, often as little as 1 micron. The technology of the invention, however, can be used to form multiple layers. The term xe2x80x9cpolymer particlexe2x80x9d typically connotes a polymer material typically made by polymerizing ethylenically unsaturated monomers and then comminuting such a polymeric material into a particle or particulate collection. The particles in the particulate can have a major dimension less than about 40 microns, preferably less than about 25 microns but preferably greater than about 10 microns. The term xe2x80x9ccoalescing agentxe2x80x9d typically connotes an organic or silicone liquid material that causes the polymer particle to coalesce into a single layer floor finish film having a dimension greater than about 1 micron but less than about 12 microns. Such coalescing agents are materials that can cause the polymer particles to flow or fuse into a continuous layer before evaporation and are typically organic materials with a relatively low VOC (volatile organic compound content), typically less than about 10 mm-Hg preferably less than 5 mm-Hg, often less than 1 mm Hg. More volatile, higher VOC coalescing agents can be used in a factory location where dying speed is important. In such locations, higher VOC coalescing agents can be recovered and recycled during coating operations. The more volatile solvent coating media carrier materials typically have a VOC greater than 20 mm-Hg and more 25 to 80 mm-Hg. A coalescing agent can be identified as a coalescing agent using the following procedure. The polymer floor finish particulate or powder material can be placed on a surface of a glass dish or microscope slide. About 0.5 grams, or less, sufficient to thinly cover the glass surface, of the slide or dish is used. Onto the particulate or powder is added about an equal amount by weight of a candidate coalescing agent. The test or candidate coalescing agent can be lightly sprayed or added drop-wise to the polymer powder and lightly mixed to form a uniform glaze of the wetted polymer. Visual and microscopic observations will confirm if the candidate coalescing agent can form a coating. The coating should be formed within about 30 minutes, preferably less than 5 minutes.
The coating compositions of the invention can be used to form a finish on an individual flooring unit. A flooring unit is defined as sheet vinyl with a defined width and an optional or indeterminate length, a single uninstalled quarry tile, composite tile, vinyl tile, wooden flooring component such as pine strips or oak strips having milled tongue and groove installation components and other common stone, thermoplastic, linoleum, wood flooring components, etc. Such flooring units are designed to be delivered to an installation site and individually installed onto a rough floor or subfloor surface using adhesive compositions, mastic, metallic fasteners such as nails, wooden pegs, etc. Such flooring units are typically used to cover a rough floor or subfloor with a large number of units to form the final floor surface.
Each flooring unit can be covered with the compositions of the invention leaving a uniform continuous coating layer. The flooring unit can comprise sheet vinyl or an individual flooring unit that can have an area that range from about 5 to 2000 cm2, more commonly 10 to 1000 cm2. The most typical flooring units comprise vinyl flooring made in the form of large rolled sheets with a width of 2 meters to 5 meters and an indeterminate length, about 5 to 6 cm2 ceramic tile, about 15 cm by 15 cm vinyl tile, quarry tile having dimensions of from about 200 cm2 to 1000 cm2 and flooring components having tongue and groove installation features that can have a width of from about 2 to about 20 cm and variable length from 25 inches to 350 cm. The surface area of each flooring unit can range from about 5 to about 5000 cm2, commonly 10 to 4000 cm2, and most commonly 20 to 1000 cm2. When used in forming a coating layer on a flooring unit, the coalescing agent and the polymer particulate are typical materials of the invention. However, the coalescing agent used in a factory formed floor finish on a flooring unit can be of higher volatility than typical coalescing agents used in field applications. Factory manufacture of coating units using higher volatility coalescing agents can involve processes in which the volatilized coalescing agents are recovered, recycled and reused in the application rendering the higher volatility less problematic than their use in field applications. Further, factory application of the coating compositions on flooring units can involve the use of relatively high heat flux of incident energy. Such high heat energy use can result in more rapid coating formation and more rapid evaporation of the coalescing agent from the finished floor unit. The use of the methods and compositions of the invention in coating flooring units involves coating one substantially planar surface of the flooring unit without applying a coating to an installation surface of the flooring unit. In other words, the surface of the flooring unit that is used to attach the flooring unit either to the rough floor or subfloor or to other flooring units is preferably not coated with the compositions of the invention. However, the exposed surface of the flooring unit obtains a complete continuous uniform coating of the compositions of the invention.
The coatings and finishes of the invention appear to the eye to be substantially identical in gross appearance and when conventionally tested have properties similar to those of the prior art. In the coatings of the invention, however, the microscopic structure of the inventive coatings of this invention appears to be substantially different. In practice, the coating layers can appear substantially different under cross-sectional microscopic examination. The prior art coatings are typically made with four or more applications of the liquid coating material forming a layered structure. This is a result of the limits of the application methods. Each individual layer has a thickness controlled by the viscosity of the liquid coating mixture. Useful viscosity materials require several applications. A coating of this invention is typically a single uniform layer structure greater than 1 micron, but typically less than 20 microns in thickness.
The polymer particulate compositions of the invention are typically substantially free of liquid organic or aqueous media, however, the coalescing agent can contain some proportion of water or solvent but rarely has greater than about 10 wt % water based on the total amount of coalescing agent. Further, the polymer particles can contain some water as a matter of impurity or residue from water based polymerization techniques, however, the amount of water present in the polymer particulate is typically less than 10 wt % of the total polymer material. Certainly, little or no free or flowable water is used as an aqueous medium or carrier liquid to carry either the coalescing agent or the polymer particle onto the floor surface. For the purpose of this patent application, the term xe2x80x9cfloor surfacexe2x80x9d typically relates to a ceramic, terrazzo, concrete, quarry tile, vinyl, linoleum, wood composite or other conventional floor surface material. The compositions of the invention are typically used to coat a large area of floor in a single step. Accordingly, the processes of the invention are typically used in coating more than about 100 cm2, preferably more than 0.9 m2, most preferably more than 10 m2, of floor surface area in a single step. Typically, the polymer and coalescent can be simultaneously applied to a surface. The compositions of the invention can also be applied using devices designed to cover 100 m2 of floor surface in a good amount of time. One of ordinary skill in the art will readily appreciate that the polymer particulate or the coalescing agent can be distributed over a relatively small or large area of floor followed by a careful application of the other part of the two-part coating systems. Such a coating technique is substantially different than the application of a solvent or aqueous based medium in which the combined one-part materials are applied typically using a mop to distribute the combined materials in a relatively small location in building up a continuous coating on the floor surface. Lastly, one of ordinary skill in the art will readily appreciate that there is a substantial difference between the form of the materials typically considered to be coatings in an aqueous media or coatings in an organic solvent media when compared to coating materials of the invention comprising a flowable powder polymeric composition and a liquid considered to be a coalescing agent. Solvents typically do not become involved in coalescing polymer particles into a final coating. Coalescing agents, however, are comparatively lower in volatility than solvents. Coalescents are intimately involved in penetrating polymer particles, causing the polymer to fuse or flow, leaving a coated surface as the coalescent evaporates. The resulting coating exhibits coverage, consistency and uniform coating properties. Commonly, solvents or other liquid carrier media evaporate without causing any important change in polymer properties. A coalescing agent operates to modify the polymer properties of a coating system during fusing and coating formation. A plasticizer is different than a coalescing agent because after a plasticizer is incorporated into a polymer it is an essentially permanent part of the formulation. A plasticizer results in a permanent change in polymer properties including Tg (glass transition temperature), rheology, tensile strength, film forming properties, etc. Lastly, the coatings of the invention are substantially free of aqueous or solvent residue in the coating layer.